With our reputation as specialist manufacturers of water filled crane test bags, we were approached to design and manufacture a bespoke 48 ton capacity bag, to be used for proof testing a winch on board a vessel being built in Asia. The winch was part of the sysem used to lower a multi-million pound deep sea diving bell, inside the vessel’s ‘moon pool’, which is the shaft running though the hull of the vessel into the ocean, though which the diving bell is lowered into the water, along with the personnel inside.

Traditionally crane test bags are specifically designed and developed to form a ‘tear drop’ shape when filled with water, to assist with spreading the load evenly across the PVC coated polyester material and supporting harness arangement. However, with the ‘moon pool’ shaft, it required us to adopt a non-standard cylindrical design, in order to reach the desired 48 ton capacity load inside the available space. This also required us to incorporate several circumferential strengthening bands, to ensure that during the actual dynamic winch test, the increased levels of hoop stress being introduced because of the cylindrical design were catered for. The concept and test itself were very successful, and we have been called upon on a number of similar projects.